Movement of objects in space is a necessary task in a typical manufacturing environment. Robotics have increasingly been employed to effect the necessary movement. However, when multiple objects are being moved, a potential for interference between the objects exists. An interference exists if the at least two objects share the same space at the same time. That is, the objects have the same coordinates with respect to a common frame of reference.
With modern industrial robots moving at considerable velocities, interferences between robots can result in a collision and undesirable damage to the robots and work pieces being handled by the robots. The collisions may lead to costly down time in the manufacturing process. Accordingly, it is desirable to avoid such collisions.
Prior art systems and methods have been used in an attempt to minimize interferences and collisions. However, there are several shortcomings of the prior art systems and methods. Typically, a tool center point (TCP) is only checked relative to a predetermined interference area (static space). For multiple robots, it is difficult to directly or effectively prevent the collision or interference thereof. Further, it is difficult to specify an interference space in respect of a static coordinate system for multiple moving robots. Any interference space is not only a function of the robot motion path, but also a function of the motion speed. Difficulty also exists in attempting to handle a deadlock situation when two or more robots request to move to a common space at the same time.
Prior art systems also attempt to prevent a TCP for a robot from colliding in a fixed space relative to its world coordinate system. When multi robots (with multiple controllers) share common spaces or so called interference spaces during a task execution, each controller has to wait until no robot is in the common spaces, and then the controller can issue the motion control commands to allow the robot to move. This process is also called a wait and move process, which generally increases working cycle time. Draw backs exist when using the prior art systems with multiple robots. It is difficult to effectively specify an interference space in terms of a fixed coordinate system, because the interference space is not only the function of the robot motion path but also the motion speed. When more than one robot requests to move to a common space at the same time, it creates a deadlock situation where none of the robots can move because they are waiting for one another.
It would be desirable to have a system and method for controlling motion interference avoidance for a plurality of robots, wherein an efficiency of operation is maximized and a potential for interference or collision is minimized.